Tibet and Mongolia are among the regions not referred to in the sources, Islamic or otherwise, as places where the call to Islam met which much success. None the less, there are some reports on certain instances of conversion among the inhabitants of the region. An ancient reference is one by the Iranian author of Hudud al-`alam, in the 4th century AH, who mentions the existence of a Muslim population as well as a mosque in Lhasa, the capital of Tibet. In fact, throughout the centuries, there was a group of non-native Muslim merchants, especially from Kansu and Tsinghai, who were active in the northeastern regions of Tibet. The date of the initial introduction of Islam in Tibet must be placed at least in the Yuan period, after Genghis Khan, if not earlier. The region of Tenduk, in southern Mongolia, which, in the Yuan period, housed populations of Christians, Buddhists and Muslims, is speculated to have been the birthplace of the Muslim race of Urghun. In northern Mongolia, as well, Rashid al-Din speaks of the presence of Muslim minorities, including in the region of Kahr Chaghan. In the early Ch’ing period, a group of Muslim merchants migrated to the interior regions of Mongolia. In 1104 AH, another wave of immigration into the region, prompted by civil wars, furthered the cause of Islam, especially in the city of Huhih Hut.